Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$67.89	6.506%	$72.3069	$72.31	$72.30	$72.30
Purchase #2	$167.41	6.754%	$178.7169	$178.72	$178.70	$178.70
Purchase #3	$132.68	6.493%	$141.2949	$141.29	$141.30	$141.30
Purchase #4	$132.39	6.272%	$140.6935	$140.69	$140.70	$140.70
Purchase #5	$91.55	13.642%	$104.0393	$104.04	$104.05	$104.00
Purchase #6	$130.95	4.161%	$136.3988	$136.40	$136.40	$136.40
Purchase #7	$151.54	11.213%	$168.5322	$168.53	$168.55	$168.50
7 purchase totals =	$874.41		$941.9825	$941.98	$942.00	$941.90